I know everyone is different but it is mix and match with me. If I have a fair bit of growth (three days or so) the 37C or the 24C with an Astra or Polsilver are great. If it is one or two days the 24c or even better the DE89 with a Voshkod takes some beating as that blade is soo smooth in those razors (for some reason not as impressive in the slant).
In regard to bumps I would say go easy and maybe try an alum block. I get flare ups on my neck too so now I just do one careful downward pass on my neck (three passes as per rest of my face is a disaster there no matter what the razor or blade) and that suffices. Also beat the hell out of your soap. I use Wickham, OSP, Nannies, Prorasso and TFS on main rotation (Phoenix and Beau sometimes in a scuttle) and I build lather in puck for at least 40 seconds until it has a yoghurt like comsistency. That gives me the required cushion.